1. Field of the Invention
The present invention relates to the control of jets of fluid. More specifically, this invention is directed to multistable fluidic switches. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention has been found to be particularly well suited for use in thrust vector steering systems. As is well known, partial or total control over the direction of travel of a vehicle employing a gas generator as a propulsive source can be achieved by deflecting or vectoring all or a portion of the propulsive gases at an angle to their normal flow axis.
Prior art thrust vector control systems may be classified as either mechanical or hydromechanical devices. Regardless of type, all prior art thrust vector control schemes have been characterized by comparatively large size and weight, inefficient utilization of control and propulsive fluids and less than the requisite reliability.
In order to obviate the problems inherently associated with prior art thrust vector control systems, and to improve upon previous hydromechanical devices, it has been proposed to borrow from the fluidics art. That is, thrust vector controls employing fluid amplifier or switch type devices have been suggested. Such fluidic devices, which often rely for operation upon well known phenomena such as the Coanda effect, while theoretically offering substantial improvement over previous technology, have not found wide usage for a number of reasons. One of the more important deterrents to non-use has been the geometry of the prior art devices. It has previously been possible to maintain deflected flow in a desired radial nozzle sector with an acceptable degree of stability only by providing oppositely disposed flat surfaces to which the flow could attach. Such restriction to two dimensional shapes has severely limited flexibility. A further and associated problem with prior art fluidic control devices has been the excessive size of such apparatus. This excessive size has resulted from both the above-discussed two dimensional geometry and also from previous design philosophy which has dictated nozzle contour which diverged away from the normal stream axis in the downstream direction from the nozzle throat. An additional problem with prior art fluidic control devices has been embodied in excessive control gas flow.
Considering further, for purposes of explanation only, the use of a fluidic switch in a thrust vector control system, it has long been considered highly desirable to achieve both pitch and yaw and additionally roll control with the same apparatus. In the prior art, however, a rotational flow component has generally been achieved only by resort to a secondary flow injection which, of course, is wasteful of control fluid.
To summarize the deficiencies of prior art fluidic devices particularly as adapted for use as vehicle thrust vector controls, such devices were excessively large, made inefficient use of control fluid, were generally lacking in stability and slow to respond to switching command signals, could provide roll control in addition to pitch and yaw control only by resort to secondary gas injection and were characterized by short life due to poor resistance to erosion by the high temperature gases flowing therethrough.